Turntable in audio and video apparatus are conventionally made of metals such as aluminum or reinforced thermosetting resins such as bulk molding compound. Because of their high dimensional accuracy, turntables made of metals or reinforced thermosetting resins have the advantage that they experience a reduced level of vibration when they are revolving at high speed. On the other hand, such turntables are so heavy that they involve a long access time before a video or audio signal materializes and that they do not have a sufficient ability to damp vibrations exerted upon the apparatus as a whole. It has therefore been desired to develop a turntable having a higher performance.
In response to this need, the present inventors attempted to develop a turntable of higher performance that is made of a shaped article of thermoplastic resin. Compared to thermosetting resins, thermoplastic resins are more easily shaped into products of thin section and hence have the potential to provide turntables of lighter weight. Furthermore, thermoplastic resins can be directly shaped into articles of a complex shape such as those having ribs or holes without requiring any special machining to make them. Because of these features, thermoplastic resins are considered to be suitable for the purpose of making turntables of higher performance. However, none of the prior art thermoplastic resins are suitable for commercial application because if they are shaped into disks with thicknesses of up to 3 mm, warpage will develop in the disks on account of internal strain and the disks do not have any satisfactory dimensional accuracy in thickness terms.
Under the circumstances described above, the present inventors conducted intensive studies to make a turntable of high performance and successfully produced the desired turntable by forming a receiving portion from a specified thermoplastic elastomer on top of a substrate that was shaped from a specified thermoplastic composite resin of higher rigidity under specified forming conditions and which displayed reduced warpage while exhibiting high dimensional accuracy in terms of thickness.